UTTAR PRADESH JOURNAL OF ZOOLOGY

The present study characterised age-related histological changes in the duodenum of Indian domestic pigs across three postnatal developmental stages. Duodenal tissue from 18 Indian domestic pigs was categorised into three age groups: Group I (piglets, 0–4 weeks; n=6), Group II (weaners, >4–10 weeks; n=6), and Group III (>10 weeks; n=6). Tissues from the duodenum were collected and fixed in 10% neutral buffered formalin and Bouin’s fluid, processed for paraffin embedding, and sectioned at 5–6 µm. Histological evaluation employed Haematoxylin–Eosin for general architecture, Masson’s Trichrome for collagen–muscle differentiation, Wilder’s method for reticular fibres, and Weigert’s stain for elastic fibres. The duodenal wall consistently exhibited four tunics (mucosa, submucosa, muscularis, and serosa) across all age groups. Duodenal villi progressed from slender, tongue-shaped structures at birth to tall, ridge-like forms with broad bases and pointed apices. Enterocytes were columnar and displayed prominent brush borders, while connective tissue support (collagen, reticular, and elastic fibres) increased from Group I to Group III. Goblet cell density and intraepithelial lymphocyte counts in the mucosa increased with age, particularly in crypt regions. Paneth cells were absent at birth but appeared from day 21 onwards and became more abundant in older groups. The lamina muscularis mucosae thickened progressively, while plicae circulares became evident from day 7 and increased in prominence with age. Brunner’s glands, sparse and isolated at birth, formed compact lobules by day 13 and dominated the submucosa in weaners and adult pigs, especially in the cranial duodenum. Connective tissue fibres intensity (collagen, reticular, and elastic) increased in all layers with advancing age. The tunica muscularis consisted of inner circular and outer longitudinal smooth muscle layers with intervening connective tissue containing myenteric plexuses, while the tunica serosa formed the outermost covering, with loose connective tissue, blood capillaries, nerves, variable adipose tissue, and external flat mesothelium. These age-related histological changes in the duodenum represent functional adaptation to postnatal digestive, absorptive, and immune demands, providing a baseline for porcine models and comparative monogastric studies.